The present invention enables the reaction between constituents of two immiscible fluids in order to produce desirable end products. This is currently achieved by making dispersions of one phase in the other to generate small droplets with a large surface area where mass transfer and reaction can occur, as described in Liquid-Liquid and Solid-Solid Systems, in Chemical Engineer's Handbook, 21-1-21-29, 5th ed., (Robert H. Perry & Cecil H. Chilton eds., McGraw-Hill 1973). Dispersions are used to wash water soluble impurities out of organic process streams, to neutralize organic process streams by extracting acid and base compounds from organic process streams, and to effect chemical reactions between components of two streams. For chemical reactions, phase transfer catalysts are frequently used to enhance mass transfer across the interface of the droplets, as described in Phase-Transfer Catalysis: Fundamentals, Applications, and Industrial Perspectives, (Charles M. Starks, Charles L. Liotta, & Marc Halpern eds., Chapman & Hall 1994). Co-solvents can also be used for this purpose.
Phase-transfer catalysis (PTC) technology is used in the commercial manufacture of more than $10 billion per year of chemicals, including monomers, additives, surfactants, polymers, flavors and fragrances petrochemicals, agricultural chemicals, dyes, rubber, pharmaceuticals, and explosives. PTC technology is also used in pollution prevention, pollution treatment and the removal or destruction of impurities in waste and product streams. PTC technology is used in these applications because it provides many compelling benefits, such benefits being primarily related to reducing the cost of manufacture of organic chemicals and pollution prevention. The many significant and advantageous process performance achievements which are routinely realized using PTC include increased productivity (increased yield, reduced cycle time, reduced or consolidated unit operations, and increased reactor volume efficiency), improved environmental performance (eliminated, reduced, or replaced solvent and reduced non-product output), increased quality (improved selectivity and reduced variability), enhanced safety (controlled exotherms and use of less hazardous raw materials), and reduced manufacturing costs (eliminated workup unit operations and use of alternative raw materials). With such a long list of highly desirable benefits achieved in commercial applications (usually multiple benefits are achieved in each application), it is no wonder that PTC technology is used in a wide variety of applications. Cost reduction and pollution prevention are the two most powerful driving forces in the chemical industry today, and they match precisely the strengths and benefits provided by PTC.
Despite these great benefits and the wide scope of applications, many chemical companies are still not using PTC technology. Probably the most difficult challenge to be met in the development stage of a PTC project is separation. Specifically, separation of phases can be difficult and time consuming since PTC catalysts resemble soaps and are interfacially active, and separation of catalysts after the reaction takes place is needed for product purity and quality.
Processing of vegetable oils typically includes the following steps: 1) acid degumming to remove phospholipids such as lecithin; 2) neutralization to remove free fatty acids that can cause rancidity in processed oils (in some processes degumming and neutralization are combined); 3) washing to remove residual caustic and soap in the neutralized vegetable oil (a double wash is often recommended); 4) bleaching to remove color bodies; and 5) deodorization. Moreover, many modern plant processes are continuous and use centrifuges to accelerate settling of oil and water layers in caustic neutralization and subsequent washing because of the formation of soap by reaction of free fatty acids and caustic, as in the PTC technology discussed above.
U.S. Pat. Nos. 3,754,377, 3,758,404, 3,839,487, 3,977,829, and 3,992,156 are directed to methods of effecting mass transfer between two immiscible fluids without forming dispersions.
U.S. Pat. No. 3,758,404 (issued to Clonts) discloses a method for effecting mass transfer between immiscible, concurrently flowing liquid-liquid phases, including a conduit having a bundle of elongated fibers positioned therein. The fiber bundle is positioned within the conduit at a perforated node that also acts as the point of introduction for the first liquid, which is deposited onto and within the fiber bundle as a film. A second liquid is directed into the conduit and over the first liquid deposited on the fibers. The large area of contact between the first and second liquids provides for an efficient mass transfer there between. The first liquid deposited on the fibers is moved along the fibers by the viscous drag occurring between the two concurrently flowing fluids. The first liquid in film form, sometimes referred to as the constrained phase, is moved along the fibers and eventually deposited in a collection vessel. The downstream end of the fiber bundle extends outwardly of the conduit into the collection vessel for the purpose of making direct fluid contact with fluid collected off of the bundle in order to prevent dispersion between the two phases. In this manner, mass transfer is efficiently effected between the two immiscible liquids without dispersion of one liquid into the other.
U.S. Pat. No. 3,754,377 (issued to Clonts) provides for a gas-liquid mass transfer process which is similar to the liquid-liquid mass transfer process just described. This patent teaches use of the fiber contactor to extract acidic components from natural gas and light hydrocarbons with aqueous caustic.
U.S. Pat. Nos. 3,839,487 and 3,977,829 (both issued to Clonts) describe use of the device disclosed therein for the alkylation of paraffin streams with olefin streams using concentrated sulfuric acid.
U.S. Pat. No. 3,992,156 (issued to Clonts) provides for mechanical improvements to fiber contactors, such as a method of supporting the fibers to prevent premature breakage and the use of multiple bundles of fibers and distribution tubes. These fiber contactors have proved to be remarkable inventions providing mass transfer at high efficiency levels without dispersion of one fluid into the other in the extraction of troublesome acidic impurities such as phenolics, hydrogen sulfide, CO.sub.2, and mercaptan compounds from petroleum refinery process streams.
In addition, U.S. Pat. No. 5,705,074 (issued to Brient) teaches the use of fiber contactors to remove phenolics and other water-soluble organic materials from aqueous refinery waste streams by an extraction process. U.S. Pat. No. 5,997,731 (issued to Saurez) teaches the use of fiber contactors to neutralize an alkaline solution containing dissolved sodium sulfides, mercaptides and phenolates with a carbon dioxide-containing solvent and recover processable hydrocarbon values. U.S. Pat. No. 5,306,831 (issued to Beshouri, et al.) teaches use of fiber contactors to remove water soluble polyol impurities in a sorbitan ester mixture by treating a polyol-containing sorbitan ester dissolved in a solution containing a hydrocarbon and a polar organic solvent with an aqueous metal halide salt solution.